Xerographic printer



June 6, 1961 w. D. BOLTON XEROGRAPI-IIC PRINTER 4 Sheets-Sheet 1 FiledDec. 21, 1955 DRIVE L MECHANISM \13 GENEVA MECHANISM RECORD CARDCONTROLLED DATA INPUT "FIG; 1.

I N V EN TOR.

BOLTO N WALLIS D.

TONER IMAGE FIXING APPARATUS BI VARIBLE SPEED CO NTROL 82 AT TOR NEYJune 6, 1961 w. D. BOLTON 2,987,037

XEROGRAPHIC PRINTER Filed Dec. 21, 1955 4 Sheets-Sheet 2 ARC CONTROLSJune 6, 1961 w. D. BOLTON 2,987,037

XEROGRAPHIC PRINTER Filed Dec. 21, 1955 4 Sheets-Sheet 3 June 6, 1961Filed Dec. 21, 1955 W. D. BOLTON XEROGRAPHIC PRINTER 4 Sheets-Sheet 4United States Patent 2,987,037 XEROGRAPHIC PRINTER Wallis D. Bolton,Vestal, N.Y., assignor to International Business Machines Corporation,New York, N.Y., a corporation of New York Filed Dec. 21, 1955, Ser. No.554,513 4 Claims. (Cl. 118-637) This invention relates in general toelectrographic printing machines and in particular to improved apparatusthereof for producing and developing latent electrostatic images.

The preferred embodiment of the invention to be described herein isadapted for use in a type of electrographic printing machine commonlyreferred to as a xerographic printer. As is well known to personsfamiliar with this phase of the graphic arts, xerography is a termapplied to a printing process in which latent electrostatic images arerendered visible, i.e. developed, by a pigmented electroscopic powder,often referred to as Xerographic toner, the resulting electroscopicpowder image thereafter first being transferred and then affixed to aprint receiving sheet so as to afford a permanent printed copy whichdepicts the latent electrostatic image exactly. An apparatus employingsuch a printing process is shown and described in Carlson Patent No.2,357,809 which issued on September 12, 1944, and follows the steps ofelectrically charging an electro-photoplate having a photoconductiveinsulating layer on an electrically conductive backing member, exposingthe charged electrophotoplate to an optical image so as to form a latentelectrostatic image thereof on the electrophotoplate, dusting the latentelectrostatic image with xerographic toner in order to develop thislatent image so that the configuration thereof is rendered visible,transferring the xerographic toner image onto a print receiving sheetsuch as paper, and finally removing any excess toner which remains onthe surface of the electrophotoplate after the preceding transfer stepbut prior to the next electrophoto plate charging step.

Another kind of xerographic printer employing a printing processsomewhat different from the aforementioned one disclosed by the Carlsonpatent, is shown and described in Schatfert Patent No. 2,576,047 whichissued on November 20, 1951. This printing machine embodies acontinuously rotating drum on which an electrically insulating imagelayer is secured. This permanent design image layer is electrostaticallycharged prior to being dusted with xerographic toner. The toner will, ofcourse, be attracted and adhere to the charged surface area of thepermanent design image layer so that when the toner supported thereby istransferred onto a print receiving sheet, the xerographic toner sotransferred will define a configuration similar to the permanent designimage layer. This latter type of printing where the image layer ispermanently formed, is commonly referred to an xeroprinting in order todistinguish the same from other types of xerographic printing. It is tobe observed that a xeroprinting machin is in essence a printingduplicator because any number of copies may be produced from a singlepermanent design image layer.

Before proceeding any further it would be Well to distinguish anelectrophotoplate from an electroplate. The former is a membercomprising a photoconductive in sulating layer on a conductive backing,whereas the electroplate is a member comprising an insulating layer,photoelectric and otherwise, on a conductive backing. Accordingly, itshould be clear that the expression electroplate includes anelectrophotoplate. For this reason, the term electroplate will be usedthroughout this specification.

The present invention is directed to-xerographicprint- 2,987,037.Patented June 6, 1961 ers generally, and has for its broad object theprovision of improved apparatus thereof for bringing about improvedxerographic printer operation.

As is stated in copending US. patent application, Serial No. 554,515,filed on December 21, 1955, by W. D. Bolton et al., it is Wellrecognized that xerography, or dryprinting as it is so often called,requires the application of pigmented powder onto the electroplatesurface in order to develop the latent electrostatic images storedthereon. This has been accomplished in the past in a number of differentways, such as by the so-called cascade developer type apparatusdescribed in the afore-mentioned Schaifert patent. The latentelectrostatic image developing apparatus described in the instantapplication utilizes a soft fur brush for transferring xerographic tonerparticles from a suitable source onto the electroplate surface. Inaddition to transferring toner particles, the soft fur brush causes anegative triboelectric charge to be imparted to those particles actuallybrought into physical contact with the brush hairs. The preferredembodiment of the present invention includes a so-called segmented softfur brush whereon toner particles are first deposited and thentransferred onto the surface of a xerographic drum by a gentle wipingaction of the brush in the direction of drum movement. Briefly, theso-called segmented developer brush includes a cylinder for supporting aplurality of spaced conducting segments on the outer periphery thereof,and a suitable fur brush which is secured to the outer periphery ofthese conducting segments in a fashion so that the brush hairs extendoutwardly. As is disclosed in detail hereinafter, the transfer of tonerparticles onto the xerographic drum surface can be governed by applyingexternal voltages to the developer brush. Thus, if any one or more ofthe segmented brush commutator segments is subjected to a positivevoltage, for example, a positive charge will be applied to the brushhairs so as to prevent the transfer of 'xerographic toner fro-m thebrush hairs onto the surface of the xerographic drum electroplate.

Accordingly, another object of this invention is to provide an improvedlatent electrostatic image developer brush.

In line with the foregoing, another object of the present invention isto provide an improved latent electrostatic image developer brush forregulating the transfer or migration of toner particles from the brushonto a charged electroplate surface.

As is recognized by persons familiar with this art, xerographic toner isan extremely difficult material to handle. This is due particularly tothe fact that the toner particles are very fine, i.e., two to twentymicrons in size, and quite tacky. Thus, to produce a successful brushdeveloper, it is necessary to provide satisfactory means for depositingthese hard-to-handle toner particles on the brush hairs evenly acrossthe full length of the brush. The aforesaid means should include thefeature whereby the amount of toner being deposited on the brush hairscan be regulated.

In keeping with the foregoing, another object of this invention is toprovide an improved toner handling device.

Another object of the present invention is to provide an improved tonerfeeding mechanism for use with a brush developer.

Another object of this invention is to provide a piston toner feedingmechanism having yielding means for depositing a regulated rate ofXerographic toner evenly on the brush hairs of a developer brush.

As stated previously, the developer brush hairs impart a negativetriboelectric charge to the toner particles that are transported from asuitable toner source to the electroplate surface. At the same time, apositive triboelectric charge is imparted to the brush hairs. Thispositive charge is apparently of a lesser magnitude, however, than isthe positive charge on the electrophotoplate surface that defines alatent electrostatic image. 1 This appears to be so for the reason thatthe toner particles adhere to the charged electroplate surface ratherthan the brush hairs. If, however, a suitable external positive chargeis applied to the brush hairs in any one of a variety of ways, tonertransfer to the electrophotoplate surface may be prevented.

Accordingly, another object of this invention is to provide aselectively operable latent electrostatic image developing apparatuswhereby the development of a latent electrostatic image may be readilycontrolled.

In line with the foregoing, another object of this invention is toprovide an improved device for regulating the migration of tonerparticles from a toner carrier ont a charged electrophotoplate surface.

Most xerographic printers known heretofore are substantially similar tothose described in the afore-mentioned Carlson and Schafiert patents inthat they are for the most part copying and/or duplicating machines.That is, the latent electrostatic image of some given object isgenerally formed by way of an optical image thereof, which image issubsequently developed and then printed in the well-known manner. It iswithin the scope of the present invention to provide an originaldocument xerographic printer which does not require optical imageapparatus for producing the latent electrostatic images. Instead, thislatter-mentioned xerographic printer causes symbols, characters andnumerals to be formed in a lineby-line fashion directly in response todata representing signals. Briefly, latent electrostatic images ofsymbols, characters and numerals are formed on the surface of anelectroplate by directing electrostatic field discharges, known commonlyas corona currents, having configurations corresponding to these data,onto the electroplate surface. This is accomplished by employing aso-called data stencil cylinder for shaping the aforesaid fielddischarges selectively in accordance with incoming data representingsignals. These signals might be transmitted from a calculator, forexample, as well as from arecord card or tape reader.

Accordingly, another object of this invention is to provide an improvedlatent electrostatic image producing apparatus.

Another object of this invention is to provide. an improved mutable dataxerographic printer.

Still another object of this invention is to provide an improvedline-by-line xerographic printer.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of examples, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

FIG. 1 is a diagrammatic view of a continuously operating xerographicprinter employing brush development.

FIG. 2 is a diagramamtic view'of the apparatus used to govern theforming of latent electrostatic images on the xerographic drum of theprinter. 7

FIG. 3 is a somewhat diagrammatic view of optical apparatus used to formlatent electrostatic images on the xerographic, drum of the printer.FIGS. 4 through 6, inclusive, are somewhat-diagrammatic views ofnon-optical apparatus used to form latent electrostatic images on thexerographic drum of the printer.

FIG. 7 is a diagrammatic view of a plural brush developing apparatus fora xerographic printer.

FIG. 8 is a somewhat diagrammatic view of a pressed cake toner addingmechanism.

FIG. 9 is a schematic showing of a brush. developer apparatus. a

. 4 A FIG. 10 is a cross-sectional view of a so-called "segmented"developer brush.

FIG. 11 is a somewhat diagrammatic view of the segmented developer brushassembly.

GENERAL DESCRIPTION Referring to FIG. 1 wherein the xerographic printerin which the preferred embodiment of this invention is shown, the metalcylinder 10 of xerographic drum 11 is mounted for rotation on a driveshaft 12 which is driven in a counterclockwise direction by an electricmotor (not shown) within drive mechanism 13 via a conventional Genevamechanism 14. This drum 11 has secured thereto an electroplate 16 whichincludes an insulating layer 17 of amorphous selenium, for example, onan electrically conductive backing member 18 of aluminum, for instance.The electroplate 16 is flexed around cylinder 10 as shown, and isattached thereto in any one of the numerous conventional ways ofattaching a printing plate to a supporting cylinder. It is important,however, that in whatever manner this attachment is made, the backingmember 18 be in intimate contact with the insulating layer 17 as well asin good electrical contact with the drum cylinder 10 which is connectedto ground potential via shaft 12.

As successive incremental areas of the insulating layer 17 are moved ina counterclockwise direction past ionproducing charging unit 19 of thetype shown and described in Carlson Patent No. 2,588,699, issued onMarch 11, 1952, the aforesaid layer 17 of dielectric material iselectrostatically charged positive. These positively charged incrementalareas are then moved past an optical image producing unit 21 (see alsoFIG. 3) which projects optical images of the text or matter to becopied, onto the electrically charged surface of photoconductiveinsulating layer 17. The apparatus by which the optical images areproduced and projected onto the surface of layer 17 of electroplate 16,will be described shortly.

Consequent upon the exposure of the photo-conductive insulating layer 17to the optical images produced by and directed from optical unit 21,latent electrostatic images thereof are produced on electroplate 16.This is for the reason that those electrically charged incremental areasof insulating layer 17 onto which light rays are directed, aredischarged, whereas those areas not illuminated by light rays remaincharged. Hence, afterthe positively charged electroplate 16 is exposedto the aforesaid optical images, positive latent electrostatic imagesthereof corresponding to the optical information projected onto thesurface of xerographic drum 11, will remain.

Continued rotation in a counterclockwise direction will cause the latentelectrostatic images appearing on electroplate 16 of drum 11 to be movedinto a latent electrostatic image developing chamber 22. This chamberwhich will be described in detail hereinafter, is one whereinxerographic toner of the general type described in'Copley Patent No.2,659,670 which issued no November 17, 1953, is applied to the exposedsurface of electroplate 16, and, of course, over the latentelectrostatic images thereon. As a result, the pigmented toner particleswill adhere to only the afore-mentioned image defining charged areas ofelectroplate 16, whereby a corresponding number of developed tonerimages which now visibly define their respective latent electrostaticimages appear on the surface of the electroplate.

A still further counterclockwise rotation of xerographic drum 11 willcause the toner images developed on the surface of electroplate 16, tomove out of developing chamber 22 and into the realm of a negativeion-producing unit 23 which is similar to afore-mentioned unit 19. Theeffect of this second electrostatic field produced by unit 23 is todecrease somewhat the magnitude of the image defining positiveelectrical charge stored in nonconducting layer 17. This is to conditionthe developed toner images being carried on the surface of electroplate16 for ready transfer onto a print receiving web 24. In

'5 addition thereto, the negative electrostatic field to which thephotoconductive insulating layer 17 is subjected, corrects anunfavorable condition known generally as selenium fatigue.

Further rotation of drum 11 causes the developed toner images thereon tomove into a xerographic toner image transfer, or printing, station,whereat a transfer roller 26 comprising a metallic conductive portion 27and an outer portion 28 of a very resilient material having a highelectrical resistance of at least power ohms per cubic centimeter, isused to transfer the xerographic toner images from the surface ofelectroplate 16 onto the surface of print receiving web 24. The transferroller 26 is similar to one shown and described in detail in copendingU.S. patent application Serial No. 419,314, filed by C. I. Fitch onMarch 29, 1954, now US. Patent 2,807,- 233. For this reason, the samewill not be described in detail herein. The print receiving web 24,which is preferably a paper strip, is advanced by conventional means(not shown) from a web supply roll 29 to a Web take-up roll 30 via theaforementioned transfer station whereat transfer roll 26 is located, anda toner image fixing station 31. The positive potential applied totransfer roller 26 causes the xerographic toner particles on the drumsurface and which define the latent electrostatic images, to migratefrom the surface of electroplate 16 to the opposite surface of printreceiving web 24. it might be Well to mention here that web 24 isadvanced at a lineal speed that corresponds to the peripheral speed ofxerographic drum 11.

In order to remove any excess xerographic toner particles that mightremain on the surface of electroplate 16 after the toner image transferbut prior to charging the incremental areas of the photoconductiveinsulating layer 17 again by ion-producing unit 19 during anothermachine cycle, a rotating plush cleaning roller 32 is positioned withina housing 33 for retaining the toner so removed from the surface ofelectroplate 16 by rolier 32. A vacuum cleaner unit (not shown) may alsobe utilized within the housing 33 in order to remove the xerographictoner caused to be accumulated therein. As is shown in FIG. 1, prior tosubjecting the incremental areas of the photoconductive insulating layer17 to the cleaning action of plush roller 32, the electroplate 16 ispreferably subjected to another negative electrostatic field produced bycorona unit 34 which is similar to afore-mentioned unit 23. A beam oflight rays from a source 36 is also projected onto the surface ofelectroplate 16 so as to assure discharge of all of the areas of thephotoconduotive insulating layer 17. The negative field produced by unit34 tends to avoid the previously mentioned unfavorable conditionselenium fatigue, and also conditions the drum surface for easy removalof the toner particles remaining on the surface of the electroplateafter transfer.

The xenographic toner images transferred onto the surface of printreceiving web 24 may be affixed thereto by any one of several knownmethods which include fixing by pressure, heat and toner chemicalsolvent. Pressure fixing rollers within unit 31 are employed in thepreferred embodiment of this invention, and a sufiicient line contactpressure of approximately 509 pounds per lineal inch of contact isemployed to cause the xerog-raphic toner supported by the surface of theweb to flow into the fibers thereof. In order to assure that the web isnot torn or mutilated by being pulled through the pressure fixingrollers (not shown), the rollers are connected to the main drivemechanism 13 so as to be rotated in step with movement of xerographicdrum 11.

LATENT ELECTROSTATIC IMAGE FORMATION As stated previously, a latentelectrostatic image of matter to be printed or copied, is created in anelectrically insulating, dielectric layer by producing electrostaticallycharged areas thereon. This may be done in any one of several ways. Forinstance, the photoconductive insulating layer 17 (FIG. 1) may initiallybe charged positive,

for example, by an ion-producing unit 19, and thereafter while stillcharged may be exposed to an optical image formed by passing light raysthrough an opaque-transparent image defining stencil. As a result, apositively charged latent electrostatic image will be produced inphotoconductive insulating layer 17 for the reasons that thoseelectrically charged incremental areas of the photoconductive layer ontowhich light rays are directed, are discharged, whereas those areas notilluminated by the light rays remain charged.

Another way touched upon briefly hereinbefore in which to form latentelectrostatic images on dielectric layer 17, is to direct thereon shapedelectrostatic lines of force, which, in turn, act to shape an ioniccurrent flow, so that a cross-section thereof will define theconfiguration of the image it is desired to store. This may beaccomplished by an electrostatic stencil xerographic printer.

Optical rec0rder.-The xerographic printer shown in FIG. 1 may beemployed as a record card controlled lineby-line optical data recorderby forming lines of character images on the surface of electroplate 16.The image pro ducing apparatus for such a line-by-line optical recorder,is similar to that shown and described in copending US. Patent No.2,726,940, issued to E. Buhler on December 13, 1955. Inasmuch as theapparatus for producing the line-by-line latent electrostatic imagesoptically is not per se a part of the present invention, the same willbe described but briefly with reference to FIGS. 2 and 3. A moredetailed description is available in the afore-mentioned copendingBuhler patent.

Referring to FIG. 3, a constantly rotating drum 41 is provided with rowsand columns of transparent characters 42 (see also FIG. 2) on an opaquebackground 43. To facilitate illustration, the background is shown to belight and the characters are dark, but it will be understood that thecharacters are transparent. An individual column of characters 42 spacedaround the periphery of drum 41, is associated with each of eightypossible print positions, one for each column of the well-known eightycolumn IBM record card. A plurality of are units 44 each comprising aplurality of electrodes 20, 30 and 40, are mounted inside drum 41 andare so aligned that there is one are unit behind each column ofcharacters 42. The electrodes 30 and 49 are arcing electrodes andelectrode 20 is a triggering electrode that is used to alter thebreakdown characteristic of the gap between electrodes 30 and 40 toinitiate arcing. Opaque barriers (not shown) are interposed betweenadjacent are units and serve the dual purpose of preventing any possibletendency of the discharge of one are to cause the discharge of anadjacent arc, and of preventthe illumination produced by one are fromfalling upon a character 42 associated with an adjacent arc unit.Reference may be had to the copending F. Demer et al. US. Patent No.2,714,841, filed on August 9, 1955, for a detailed disclosure of the areunit.

Adjacent the drum 41 and in alignment with each arc unit 44corresponding to each column of characters 42, are individual focusinglenses 46. A plurality of so-called zoning slots 47 are arranged in fivecolumns on one end of drum 41, which slots cooperate with five lightsources (not shown) that are mounted inside drum 41 and with fivephotocells 48. It is to be observed that a given char actor 42 and acorresponding Zoning slot 47 pass respective arc unit 44 and phototubes48 at the same time. The preceding elements: cooperate to emit timedpulses which are adapted by suitable circuits represented by block 57 tocooperate with other timed pulses derived from the sensing of theafore-mentioned record cards 45, so as to effect a selective triggeringof the individual are units 44 as select characters 42 pass betweentheir arc units and respective focusing lenses 46. As a result, acharacter shaped light beam will be passed through a lens 46. Aphotoemissive material plate 49 is arranged to be exposed to the lightemitted from an arc unit, shaped by the character stencil and passedthrougha corresponding lens 46. Hence, upon exposure to light, the plate49 will emit'a cloud of electrons whose cross-sectional configuration issimilar to that of the shaped light beam passing through its lens 46.These electrons are attracted toward a high potential plate 51 connectedto battery 55. A web 52 made of dielectric material is interposedbetween photoemissive plate 49 and high potential plate 51 so that asthe electrons emitted from plate 49 are attracted toward the highpotential plate 51, they are deposited on web 52 as a latentelectrostatic image of the corresponding optical image. The web 52 ofdielectric material is thereafter passed through a toner imagedeveloping chamber 58 whereat the latent electrostatic images aredeveloped, and prior to being permanent aflixed to the web byelectrically heating units 53. a

In summation, a latent electrostatic image of a character 42 on theperiphery of drum 41 is caused to be formed when corresponding datarepresenting pulses from photocells 48 and record card reading station54 operate circuits represented by block 56 which, in turn, elfect theoperation of associated arc control circuits 57 in order to fire selectare units 44. That is, assuming that record card sensing brush 37 forreading the second card column, detects punched holes indicative of theletter A, this information will be storcd in circuits 56. Thereafter,when phototubes 48 detect zoning slots 47 which are also indicative ofthe letter A (it will be recalled that at this time the corresponding.characters 42, i.e., the letters A, are aligned with their respectivearc units 44), the coincidence of information from phototubes 48 and thesecond record card column will cause a triggering signal to be directedfrom circuits 57 via line 38 to electrode of the arc imit 44 associatedwith the second record card column. The ensuing arc will cause a latentimage of a letter A to be formed on dielectric web 52 at a positionaligned with the arc unit 44 that was fired. Other latent images may beformed in a similar fashion, and then may be developed and fixed asafore-desoribed.

Non-optical recorder.A non-optical, line-by-line xerographic printerdoes not require the ion-producing unit 19 (FIG. 1) for reasons tobecome clear shortly. A stencil cylinder 61 (see also FIG. 4) andassociated apparatus would replace previously described cylinder 41 andits associated apparatus (FIG. 3), and would be continuously rotated bydrive mechanism 13 (FIG. 1) so that the stencil cylinder would completea single revolution for each aforementioned line-by-line movement ofxerographic drum 11. The xerographic drum is also driven by drivemechanism 13, but via a conventional Geneva mechanism 14. It is by wayof the Geneva mechanism 14 that the continuous rotational movement ofthe stencil cylinder is correlated to the step-by-step movement ofxerographic drum 11. Referring to FIG. 4, stencil cylinder 61 is asomewhat thin-walled conductor supported at each end by two hubs (notshown) which may be rotated about a stationary hollow shaft 62 throughwhich wires are passed. The preferred embodiment of this inventionincludes a stencil cylinder having eighty columns ofcircircumferentially disposed characters 63 (see also FIG. 4), one foreach column of the well-known IBM record card, which eighty columns ofcharacters are identical and are similarly disposed to provide rows ofidentical characters extending lengthwise on the periphery of the drum.The characters might be comprised of a plurality of holes as depicted bystencils 63a (FIG. 6) or a plurality of prearranged slits as depicted bystencils 63b.

Secured to stationary hollow shaft 62 within cylinder 61 is a singlecorona discharge unit 64 including a corona wire 66 which runs thelength of cylinder 61. As a result, when electrical power is applied towire 66, a corona field discharge is directed through a channeledopening 67 in unit 64, which extends the full length of cylinder 61,towards the inner surface of stencil cylinder 61. Normally, this coronafield discharge is .prevented from passing throughthe stencil charactersin stencil cylinder 61 for the reason that all eighty pairs of controlelectrodes 68 (see also FIG. 5) associated with each' columnar positionof stencil drum 61, are normally biased electrically to a potential ofapproximately -800 volts. 1 Connecting wires for each of these controlelectrodes are shown in FIG. 5, and are run within hollow shaft 62.Thus, since the conductive backing member 18 (see also FIG. 1) is atground potential, as mentioned previously, and inasmuch as the coronafield discharge from unit 64 (FIG. 3) is a positive one, the fielddischarge will normally be divided into approximately separate pathswhich include the eighty pairs of highly negative control electrodes 68(FIG. 5). It should be pointed out that electrostatic field barrierplates (not shown) are used to divide opening 67 into eighty separatedopenings corresponding to the number of characters on stencil cylinder61. This is to prevent a lateral deflection of the corona dischargefield from one character position to another position. At a time that aselect character stencil 63 is aligned with the channeled opening 67 inunit 64, a positive potential in the order of approximately +800 voltsis caused to be applied to the pair of corresponding character positioncontrol electrodes 68. This action causes the positive corona fielddischarge to pass through the opening 67 defined by the afore-mentionedelectrostatic barrier plates and the oppositely placed columnar controlelectrodes 68 each of which is raised to +800 volts, through thecharacter stencil 63 aligned therewith, and onto the previouslyuncharged surface of the dielectric layer 17 (FIG. 1) on electroplate16. The afore-mentioned barrier plates '(not shown) will restrict such afield to a region opposite the select character stencil. During acomplete revolution of cylinder 61, a line of characters as depicted bylatent electrostatic images thereof may be formed before the xerographicdrum 11 is advanced one line position. This non-optical xerographicrecorder might be a record card controlled machine governed in a mannersimilar to the way in which the optical recorder (FIGS. 2 and 3) isgoverned. That is, consequent upon the coincidence of record cardindicia and zoning slot data generated as a result of the position ofthe stencil cylinder 61 (FIG. 5) relative opening 67, a suitablenegative voltage generator would be triggered ofi and a positive voltagegenerator trigged on. There would be one such positive voltage generatoras well "as one such negative voltage generator for each characterposition, i.e., for each pair of control electrodes 68. Connections fromthese generators to the control electrodes would be completed via thewires within hollow shaft 62. As stated previously, it is within theconcept of this invention to provide such a nonoptical line-by-lineprinter which would transcribe data directed from a calculator. Thus,consequent upon the coincidence of calculator output data signals andzoning slot data generated as a result of the position of the stencilcylinder 61 relative opening 67, a suitable positive voltage would beapplied to a pair of control electrodes 68.

ELECTROSCOPIC TONER In xerographic printers, latent electrostatic imagesare developed by applying an electroscopic or xerographic toner to thesurface of the insulating material whereon said latent images appear.The constituent make-up and characteristic properties of this toner thatmake the same suitable for developing such latent electrostatic images,are described in Copley Patent No. 2,659,670 which issued on November17, 1953. One of the most important properties of xerographic tonerresides in its property to become charged triboelectrically. Thus, theconstituent toner and carrier parts of an electroscopic or xerographicdeveloper, such as is described in Walkup et al. Patent No. 2,638,416which issued on May 12, 1953, are selected in accordance with theirtriboclcctric properties so that when brought into mutual contact, one

the other material part, e.g., the toner, is charged negative if thefirst material part is above it in the triboelectric series. The carrierparticles may be of a size in the order of 30 to 60 mesh, so that theseparticles will flow easily over the electroplate by gravity. As broughtout in the afore-mentioned Schaifert patent, satisfactory latentelectrostatic image development is obtainable by cascading xerographicdeveloper comprised of carrier and electroscopic toner over the surfaceof the electroplate whereon the latent images are formed. However,experimental and field use to date has very decidedly shown that thecomparatively large and hard granular carrier particles have adeleterious efifect on the surface of the insulating layer 17 (FIG. 1)of the electroplate 16 due to abrasion. This is particularly the casewhen delicate amorphous selenium is used as the insulating layer.

BRUSH DEVELOPMENT Introduction-4t has already been brought out thatxerographic developer includes comparatively large and hard granularcarrier particles as well as fine electroscopic toner particles. It hasalso been brought out that physical contact between the carrierparticles and the toner particles causes a triboelectric charge of onepo larity to be imparted to the toner and of the other polarity to thecarrier particles. The toner charge is such as to be electricallyopposite to the charge which defines the latent electrostatic imagesappearing on the insulating layer of the electroplate. In brushdevelopment to be described herein, a soft fur brush is used in place ofthe coarse granular carrier particles necessary for cascade development,to impart the necessary triboelectric charge to the toner particles. Itis by the somewhat vigorous agitation of the soft fur brush hairsrelative the xerographic toner particles that the triboelectric chargeis imparted to the toner particles. It might be well to mention herethat the brush hairs per se also have a triboelectric charge impartedthereto but of the opposite polarity to the afore-mentioned carrierparticles. As is to be expected, the brush is also used to convey tonerparticles from a suitable source of toner supply to the surface of theinsulating layer of the electroplate whereon the latent electrostaticimages are formed.

GeneraL-Referring to FIG. 9, the principle of brush development as it isnow understood in its simplest form may be explained quite easily. Abrush 71 of either beaver or red fox skin, for example, is secured to arotatable drum or cylinder 72 which, in turn, is so arranged that thenon-conducting brush hairs 73 move through a mass of xerographic toner74 in a source reservoir 76, and also in physical contact with thesurface of a dielectric layer of an electroplate 77. The physicalcontact, and resulting agitation, between the brush hairs 73 and thetoner particles 74 causes a triboelectric charge to be imparted to thetoner particles so acted upon. The use of a fur skin such as the beaveror the red fox referred to hereinabove, as well as use of xerographictoner such as described previously, causes a negative triboelectriccharge to be imparted to the toner particles and a positivetriboelectric charge to be imparted to the brush hairs. Thus, asincremental areas of the insulating layer of electroplate 77 havingpositively charged latent electrostatic images thereon, are subjected tothe negatively charged toner particles 74, the charged particles arecaused to adhere to the positively charged surface areas of electroplate77. As a result, the said latent electrostatic images are renderedvisible and are caused to be developed. It should be evident that theuse of a soft fur brush in place of the granular carrier particleseliminates the deleterious abrasive action of the carrier particles,particularly as they tumble over the delicate surface layer of anelectroplate such as amorphous selenium.

The application of brush development in a xerographic printer is shownin FIG. 1. A continuously rotating brush 71, the conventional drive forwhich is not shown} is moved in a clockwise direction at a greater speedthan is the drum 11 so that the brush hairs 73 effect a gentle wipingaction relative to the insulating layer surface of electroplate 16 inthe direction of drum movement. For example, the peripheral speed of thedrum 11 can be 700 inches per minute, whereas the speed of the brushhair ends can be 1700 inches per minute. These brush hairs 73 initiallypick up, or have deposited thereon, toner particles 74 from the orificeend of a piston-type toner feeding mechanism 81. Then, during the courseof clockwise movement of brush 71, the toner particles so depositedcontact the fur brush hairs 73, whereby a negative triboelectric chargeis imparted to these particles. Brush agitator rods 86 (see also FIG.10), or the like, are normally used in order to effect a better and moreintimate contact between the individual toner particles and the brushhairs. Finally, as the negatively charged toner particles aretransferred from brush 71 onto the surface of electroplate 16, there isof course adherence to the charged surface thereof due to an attractionbetween the positively charged latent electrostatic images and thenegatively charged toner particles.

TONER FEEDING DESCRIPTION Piston feeding device.--Those persons familiarwith this art are aware that xerographic toner is an extremely difficultmaterial to work with, because among other things, it is so extremelyfine and tacky. In a cascade type developer of the afore-mentioned typedisclosed in afore-cited Schaffert patent, it is necessary to add abatch of toner to the developer from time to time. On the other hand, byemploying a toner feeding device such as is shown and described incopending U.S. patent application, Serial No. 496,833, filed on March25, 1955, by H. Dunn, now US. Patent 2,779,306 the toner may be addedcontinuously and the amount of toner in the de veloper may be kept at aproper level. However, such a toner feeding device does not appear to beadaptable for use with a brush developer apparatus. For one thing, thebrush is comparatively long and requires toner to be added along itsfull length. For another thing, the toner added this way exceeds theamount actually required.

t should be pointed out that the problem is not solved simply by causinga developer brush to move through a batch of toner. The principal reasonis that before very long the brush will form channels or scooped outareas in the batch of toner which will remain as such unless there issome additional toner agitating action.

Xerographic toner can be supplied to the fur brush hairs 73 veryadmirably via the aforementioned piston feed mechanism 81 (FIG. 1). Thismay be done at a rate which may be varied either manually orautomatically. That is, a variable speed control apparatus 82 which isdriven by motor 84, may be manually governed in order to change the rateof advancement of piston 83 and therefore the amount of toner beingdeposited on the brush hairs from the toner tube or chamber via itsdischarge orifice. On the other hand, if a suitable photoelectricapparatus is used to detect the density of the developed toner image onthe surface of the xerographic drum 11, this photoelectric apparatusmight be used to govern a variable speed control apparatus forcontrolling the rate of movement of piston 83. In either case, thepiston shaft 75 which is loosely connected to piston 83, is connectedfor rotation to a screw 85, which, in turn, is meshed to a drive gearthat is secured to a shaft projecting from the variable speed controlapparatus 82. It is within the concept of the present invention toemploy a suitable slip clutch of any conventional design between thepiston 83 and its drive mechanism, e.g., within the speed controlapparatus 82, so that the said piston will be yieldingly urged towardthe discharge orifice end of the toner container body, which orifice is1 1 substantially the length of the brush 71. Thus, should for somereason the brush hairs not remove as much toner as is being fed by thepiston feed mechanism, there would be a sufficient back force caused bythe compression of the toner to prevent any further advancement of thepiston 83 while the aforementioned clutch slipped.

Toner adding device.-Referring to FIG. 8, a pressed cake of toner 105 ispositioned within a piston feeding device 106 comprising a piston 107for pushing the toner cake through its body container or chamber 108, apiston driving member 109, and a drive shaft 110. This shaft 110 issupported by a bushing 111 in frame member 112, and is secured to apulley 113 which is operated by a suitable drive means (not shown).Furthermore, the shaft 110 is engaged with piston driving member 109 atthreaded bushing 114. Thus, as pulley 113 and shaft 110 rotate slowly,piston 107 is pushed to the left by slowly advancing member 109.

Glass fiber brush 115 is rotated via the belt and pulley arrangement116, and is used as a toner abrasive. This brush is also caused to walkrelative a stationary rack 117 which is in mesh with gear 11.8 while thesaid gear is caused to rotate by the belt and pulley arrangement 119. Itshould be clear now that gear 118 is secured to shaft 120, whereas beltand pulley 116 are loosely supported by the shaft.

The toner cake 105 is one which can be molded at a pressure ofapproximately 5000 pounds per square inch. lIf the toner adding deviceis to be used with a brush developer apparatus, this toner cake shouldbe as long as the brush. .Thus, as the rotating glass fibers 115 movealong the exposed end of the toner cake, toner particles thereof aredeagglomerated and caused to fall into a suitable container such asreservoir 76 of FIG. 9 or be deposited onto the brush hairs. Thearrangement for moving the toner abrasive brush 115 relative the lengthof the cake of toner includes a drive pulley (not shown) for supportingpulley 119. This drive pulley is secured to a shaft (not shown) that hasa clutch (not shown) at each end for connecting the said shaft to eachofa pair of drive motors (not shown) operating in opposite directions.This arrangement also includes a pair of microswitches, one at each endof the rack 117 for governing the operation of an associated clutch.Thus, when the gear 118 has been moved to one end of rack 117, amicroswitch is operated to cause the engaged clutch to disengage and thedisengaged clutch to engage. As a result, the gear 118 is rotated in theopposite direction, and the brush 115 is caused to move back relativethe long end of pressed toner cake 105. When the gear 118 has been movedall of the way back, another microswitch is operated, to thereby reversethe rotation of gear 118 once again.

LATENT IMAGE DEVELOPING CONTROL The brush 71 (FIG. 1) is shown to besecured to a rotatable cylinder which has an electrically conductivecylinder 65 attached thereto for supporting brush 71 within anelectrically conductive shell 88 whose inner surface is always inphysical contact with brush hairs 73 of brush 71. By applying a positivepotential to this electrically conductive cylinder 65 or shell 88, e.g.,+3000 volts, being careful, of course, to electrically isolate theelectrified parts from ground, the transfer of toner particles from thebrush hairs 73 onto the latent electrostatic image bearing surface ofelectroplate 16 is prevented. The action that takes place to precludetoner transfer is not too clear, although it is believed that theapplied high positive potential imparts a positive charge to the brushhairs which therefore have a greater attraction for thetriboelectrically charged negative toner particles than do thepositively charged latent electrostatic images appearing on the surfaceof the xerographic drum. Whatever the explanation may be, it is a knownfact that toner transfer suppression, and therefore print selection,maybe eflected 12 simply by closing switch '89 so that either shell 88or conductive cylinder is subjected to the necessary positive voltage.

As has just been disclosed, the application of a positive charge orpotential onto the hairs of an image developing brush via an electrode,such as shell 88 or the brush mounting shell 65 for example, will aifectthe latent electrostatic image developing operation. Whereas a potentialof approximately +3000 volts may be applied to shell 88 so as toelectrify or charge the brush hairs 73, the developing brush shown inFIGS. 10 and 11 may be electrified or charged at various select pointsthereof via commutator segments 93. As is shown in FIG. 10, theconducting commutator segments 93 are each embedded in a'suitableinsulating member or notched cylinder 94 which, in turn, is secured formovement to rotatable member 95. Furthermore, the commutator segments 93are in direct contact with the under side of non-conducting pelt 96which, in fact, is the backing layer for the non-conducting brush hairs73. Of course, the pelt 96 need not be a continuous piece but instead aplurality of separated brushes can be used, one for each conductingsegment. The application of a voltage to select ones of the plurality ofcommutator segments. 93 may be used to govern the latent electrostaticimage developing operation of the brush developer. For example, a highpositive potential might be applied to each of the moving segmentsbrought into alignment with the radial lines 97 and 98 so as to preventthe escapement of xerographic toner in the form of a toner cloud at theend points 97a and 98a of contact between the brush hairs and theelectroplate surface. On the other hand, the application of a suitablenegative voltage to a commutator segment 93 lying between the radiallines 97 and 98, would cause an increase in the density of the developedtoner image. It might be pointed out here that there might also be anincrease in the density of the image background. Notwithstanding thislatter point, however, it is significant that there would appear anincrease in image density with the application of a negative voltage tothe commutator segment between the afore-mentioned radial lines. Onceagain, it is not too clear just what the physical action is that takesplace to cause the aforedescribed results actually realized. Oneexplanation for this behavior, however, might be that the triboelectricaction between the xerographic toner particles and the brush hairs, suchas those found in theskins of beaver or red fox for example, producesnegatively charged toner particles and positively charged brush hairs.When these brush hairs are subjected to an outside positive voltage, thenegatively charged toner particles are simply attracted much more tothebrush hairs than to the latent electrostatic images so as to prevent themigration of the negatively charged toner particles to the charged imagedefining areas on thesurface of the electroplate. This is probably forthe reason that with the application of an external positive potentialto the brush, the brush hairs are charged to a higher positive valuethan are the latent electrostatic image areas. On the other hand, theapplication of a negative potential to the brush hairs repels thenegatively charged toner particles so that more toner particles arecaused to be attracted to and/or driven towards, the positively chargedimage areas of the electroplate. In fact, the slightly positive residualpotential of approximately 50 volts which nearly always appears toremainin the background areas of the latent electrostatic images on theelectroplate, attracts more of these negatively charged toner particleswhen the brush is subjected to a negative voltage. There appear to bemany possible uses for a segmented toner brush, and many more arecertain to be realized and understood as the chemical and physicalproperties of natural and synthetic fur brushes as well as electroscopictoners, are understood. H

The distributor for the segmented brush, is shown in FIG. 11, Each ofthe conductive segments 93 is con nectedv to a respective wipingelectrode 93a. A stationary 13 disc having wiping electrodes 93bprotruding therefrom, is freely arranged over the brush shaft 131. Anyone or more of the electrodes 93b may be connected to a suitable voltagesupply, whereby a voltage will be applied to each conducting segment 93as it passes a given point.

Brush stippling-As is disclosed and claimed in the afore-mentionedcopending Bolton et al. patent application, improved toner images havebeen realized by stippling the rotating developing brush relative to thesurface of the electroplate whereon the latent electrostatic images areformed. The stippling action is performed by moving brush 71 (FIG. 1)towards and away from the electroplate 16 so that the hairs 73 thereofare caused to produce a patting or powdering action relative theelectroplate surface. It has been found that good results are obtainableby moving the brush 71 from one limit whereat the brush hair ends arebarely in contact with the electroplate surface to another limit whereatthe brush has been moved radially towards the xerographic drum along aline defined by the brush and xerographic drum centers, a dis tance ofapproximately This is not to be taken as a limitation but rather as anexample. It will be clear to those persons having ordinary skill in theart that other arrangements and/or parameters might be employed toproduce a satisfactory stippling action.

It has been found that a rate of 1200 stipples per minute is veryeffective for good image development. This, for all practical purposesand within presently known engineering limits, appears to be independentof the xerographic drum rotational speed. However, once again, theforegoing is not to be taken as a limitation in view of the fact thatacceptable results are obtainable when the stippling action occurs at arate other than 1200 per minute. It is believed that brush stippling isas effective as it is because the uniformity of toner particle chargedepends on the effectiveness of agitation between the brush hairs andthe toner. During the course of the stippling action, the brush becomesfully extended in the direction of oscillation so as to afford a violentmotion which is believed necessary to realize the desired toner charge.The toned brush, i.e., the toner applying brush, is rotated slightlyfaster in the direction of movement of the xerographic drum 11 than isthe peripheral surface speed of the xerographic drum. Thus, the freshlytoned brush hairs 73 are presented in a wiping motion in the directionof drum movement to every portio'n of the surface whereon the latentelectrostatic images are to be found. Since the stippling action is in adirection substantially normal to the xerographic drum surface, thebrush hairs bend randomly upon contact with the surface. The over-alleffect is to produce a combined patting-wiping action relative theelectroplate surface. -As a point of interest in this general field, anextremely rapid developer brush rotation without a stippling action,produces a dense cloud of toner particles. By operating the rapidlyrotating brush in grazing contact with the surface of the electroplate,the resulting developed toner image closely resembles one form by powderclo'ud development.

Plural brush developing-As is brought out in copending patentapplication Serial No. 554,514, filed on December 21, 1955, by T. Hider,it has been found that at higher printing speeds improved printed copysuch as appears on the surface of web 24, for example, may be had byemploying a plurality of developing brushes. Various brush arrangementsmay be used depending upon the physical design limitations of theprinter as well as the requirements for the printed copy desired.Referring to FIG. 7, the first toned brush 99 is employed to develop thelatent electrostatic images on the surface of electroplate 101 in themanner described hereinbefore. The second toned brush 102 is similarlyused, and may be spaced apart from the first brush approximately 6 to 8inches, for example. A developed toner image is produced by the gentlepatting-wiping action of the first brush 99 relative the surface ofelectroplate 101. The

99 and 102 for example, along with a sci-called toner backgroundremoving brush 103. This latter-mentioned brush is one which is similarand is operated similarly in all respects to the brushes 99 and 102except for the fact that the hairs of brush 103 are not moved through atoner source in order to add more toner to the surface of electroplate101. Instead, brush 103 is caused to run dry" as it were, and to contactonly the surface of electroplate 101 whereon there is a toner imagealready. There is, however, a potential of approximately +600 volts to+1000 volts applied to the hairs of brush 103. As a result, it has beenfound that such use of a brush 103 permits the removal of nearly all,and for practical purposes, all of the background toner withoutnoticeably altering the toner density of the developed images, therebyproducing a clear, clean background printed record.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in theart, without departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. A brush developing device for use to develop latent electrostaticimages stored in a dielectric member, comprising an electricallyinsulating member; a plurality of spaced conducting segments positionedon and supported by said member; a latent electrostatic image developingfur brush comprising a non-conductive layer and fibers extendingtherefrom, said non-conductive layer being secured to and in electricalcontact with said conducting segments; means for moving said insulatingmember so as to move said developing brush relative to the surface ofsaid dielectric member; a source of DC. potential; and distributor meansassociated with said moving means for connecting said source ofpotential to difierent select ones of said conducting segments.

2. A brush developer device for use in the latent electrostatic imagedeveloping station of an electrographic printer to deposit electroscopicto'ner onto the surface of the printing member whereon the latentelectrostatic images are stored, comprising an electrically insulatingcylinder; a plurality of spaced conducting segments positioned on andconnected to said cylinder; a latent image developing fur brushcomprising a non-conducting layer and fibers extending therefrom, saidnon-conduoting layer being attached to and in electrical contact withthe outer peripheral surfaces of said conducting segments; a source ofpotential; and distributor means for connecting said source of potentialto select ones of said conducting segments.

3. For use in a xerographic printer including a xerographic drum havingan insulating layer supported by a conductive plate backing therefor,the combination of an electrically insulating cylinder; a plurality ofspaced conducting segments positioned on and connected to said cylinder;a latent electrostatic image developing fur brush comprising anon-conducting layer and fibers extending therefrom, said non-conductinglayer being secured to and in electrical contact with the outerperipheral surfaces defined by said segments; a source of DO voltage;electrical circuit means for connecting one side of said D.C. source tothe said conductive plate of said xerographic drum; and distributormeans for connecting the other side of said D.C. source to select onesof said conducting segments.

15 4. For use in a xerographic printer having a rotating Xerographicdrum for storing positive latent electrostatic .images, said drumincluding an insulating layer supported by a conductive plate backingtherefor, the combination of a notched electrically insulating cylinder;a plu- 6 rality of spaced conducting segments connected to said cylinderand positioned within the notches thereof; a

a latent electrostatic image developing fur brush comprising anon-conducting layer and fibers extending therefrom, said non-conductinglayer being secured to and,

in electrical contact with the outer peripheral surfaces of saidconducting segments; a source of DC. voltage; electrical circuit meansfor connecting the negative side of said D.C. source to said conductiveplate; a distributor member connected to the positive side of said D.C.

UNITED STATES PATENTS Lowe Feb. 12, 1867 Vaughan July '10, 1883 Saunderset al. 2.; June 5, 1906 Pino 1-; ;Aug.'6, 1929 Carlson Sept. 12, 1944Dulken et a1. Feb. 6, 1945 Thomas Oct. 15, 1946 Thomas Apr. 17, 1951Ewing et a1. June 15, 1954 Mayo et al. .July 27, 1954 Buhler Dec. 13,1955 Young etal. Jan. 31, 1956 Carlson Sept. 4, 1956 Gundlach Jan. 15,1957 Grieg Oct. 29, 1957 Hayford Apr. 7, 1959 Vyverberg May 12, 1959FOREIGN PATENTS Great Britain, 1899

